The basic goal of this research proposal is to understand the mechanism of fetal gene expression activated by neoplastic transformation of adult tissues. Experiments have been designed to answer a number of fundamental questions about the mechanism of placental alkaline phosphatase expression in normal and neoplastic tissues. Construction of a probe to study gene structure and messenger RNA content is basic to this proposal. Three strategies have been designed to accomplish this goal. What is the genomic organization of the placental ALP gene and does it differ in tumors? Studies designed to answer these questions include: extensive restriction nuclease and R-Loop analyses of genomic DNA clones, investigation of the genomic organization of the placental ALP gene in normal cells and tumor cells, and, estimation of the reiteration frequency of the gene in the haploid chromosome to detect multiple allelic genes. How is the expression of placental ALP normally controlled in differentiated cells and how does neoplastic transformation activate its expression? Hybridization experiments with cloned placental ALP sequences will allow an estimate of placental ALP gene transcription in cells. Similar studies in a variety of tumor cells will allow us to determine if placental ALP gene expression invariably accompanies neoplastic transformation. Studies of genomic organization and reiteration frequency will allow an assessment of the state of the gene in tumor cells, whether the multiple forms of placental ALP result from post-translational modifications or from differences in coding sequences of the messenger RNA will be approached by structural studies of the primary in vitro translation product, programmed by messenger RNAs from tumor cells.